Systems and methods for laser spacing compensation in laser printing devices

ABSTRACT

A method includes providing pixel data that comprises lines of pixel data and shared lines of pixel data, where the shared lines of pixel data are configured such that a first laser and a second laser of a plurality of lasers within a laser printing arrangement will print the shared lines of pixel data during printing of an image on a print medium. The shared lines of pixel data are split between the first laser and the second laser such that two shared lines of pixel data allow for printing of a single line of the image to be printed. During printing, the first and second lasers fire in accordance with lines of the shared lines of pixel data, where the firing of the second laser begins printing of lines of the image and the firing of the first laser completes printing of lines of the image.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. Patent Application No.61/250,136, filed Oct. 9, 2009, entitled “Laser Spacing Compensation,”the entire specification of which is hereby incorporated by reference inits entirety for all purposes, except for those sections, if any, thatare inconsistent with this specification.

TECHNICAL FIELD

Embodiments of the present disclosure relate to the field of laserprinting devices, and more particularly, to addressing issues related tospacing between lines of printed data during sweeps of lasers duringprinting.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventor, to the extent it is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

In a laser printer, printing is achieved by first scanning a digitizedimage onto an optical photoconductor (OPC). Typically, the scanning isperformed with diodes, e.g. laser diodes or light emitting diodes thatpulse a beam of energy onto the optical photoconductor. The opticalphotoconductor typically comprises a movable surface coated with aphotoconductive material capable of retaining localized electricalcharges. The surface of the optical photoconductor is a continuous areawhere the surface is logically considered to be divided into small unitscalled pixels. Each pixel is capable of being charged to a givenelectrical potential, somewhat independent of the electrical charge ofeach surrounding pixel.

In operation, the pixels are first charged to a base electrical chargeas the pixels move past a charging unit during each revolution of theoptical photoconductor. Then, as the pixels move past the laser diodes,a beam of energy, e.g. a laser, is pulsed to remove electrical chargefrom selected pixels. The unaltered and altered pixels thus form animage on the optical photoconductor. One portion of pixels will attracttoner, while the other portion will not based on various factors such asthe electrical potential of the toner. However, since the lasers have aGaussian beam intensity shape, the edges of the lasers do extend pastthe logical rectangular pixel location so adjacent pixels do interact toa certain extent.

The toner is then transferred to a print medium, e.g. paper,transparency, and fabric. After the toner is transferred to the printmedium, the toner is affixed thereto. Any residual toner on theequipment is then removed by a cleaning station.

Generally, laser printing devices include multiple laser diodes tocreate multiple lasers for printing as previously described. Images areprinted by moving at least one of the optical photoconductor and/or thelaser diodes relative to one another repeatedly, thus resulting insweeping of the lasers relative to the optical photoconductor. The printmedium and the optical photoconductor are also moved relative to oneanother to print the image onto the print medium. Mirrors are often usedbetween the laser diodes and the optical photoconductor.

FIG. 4 schematically represents a set of printed lines 400 created bythree sweeps of lasers associated with eight laser diodes. In theexample of FIG. 4, each sweep of the eight laser diodes causes eightcorresponding lines to be created as represented by lines 1-8.Undesirable visual artifacts, such as gaps or overlaps, can occur inbetween sweeps of the lasers. For example, as shown in FIG. 4, a gap 402exists in between (i) the eighth printed line created during the firstsweep of the lasers and (ii) the first printed line created during thesecond sweep of the lasers. Also, an overlap 404 is present in between(i) the eighth line created during the second sweep of the lasers and(ii) the first printed line created during the third sweep of thelasers.

SUMMARY

In accordance with various embodiments of the present disclosure, amethod includes providing pixel data corresponding to an image to beprinted on a print medium. The pixel data comprises lines of pixel dataand shared lines of pixel data, where the shared lines of pixel data areconfigured such that a first laser and a second laser of a plurality oflasers within a laser printing arrangement will print the shared linesof pixel data during printing of the image on the print medium. Theshared lines of pixel data are split between the first laser and thesecond laser such that two shared lines of pixel data allow for printingof a single line of the image to be printed. The method further includesprinting the image, where printing the image includes repeatedly movingthe plurality of lasers and the optical photoconductor (OPC) relative toone another and, while moving the plurality of lasers and the OPCrelative to one another, firing the plurality of lasers in accordancewith the lines of pixel data and the shared lines of pixel data.Additionally, printing the image further includes moving the printmedium and the OPC relative to one another. During moving of theplurality of lasers and the OPC medium relative to one another, thefirst laser fires in accordance with lines of the shared lines of pixeldata and the second laser fires in accordance with lines of the sharedlines of pixel data, where the firing of the second laser beginsprinting of lines of the image and the firing of the first lasercompletes printing of lines of the image.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure will be readily understood by thefollowing detailed description in conjunction with the accompanyingdrawings. To facilitate this description, like reference numeralsdesignate like structural elements. Embodiments of the disclosure areillustrated by way of example and not by way of limitation in thefigures of the accompanying drawings.

FIG. 1 is a schematic diagram of a laser printing device, in accordancewith various embodiments of the present disclosure.

FIG. 2 is a schematic diagram of a printing arrangement of the laserprinting device of FIG. 1, in accordance with various embodiments of thepresent disclosure.

FIG. 3 is a schematic diagram of a video channel of the printing portionof FIG. 2, in accordance with various embodiments of the presentdisclosure.

FIG. 4 is a schematic view of a set of printed lines from a laserprinter, in accordance with a prior art method.

FIG. 5 is a schematic view of a set of printed lines from a laserprinter, in accordance with various embodiments of the presentdisclosure.

FIGS. 6-9 are graphs of desired output for a single, non-overlappedlaser versus time and the same data alternately being output to twoseparate overlapping lasers, in accordance with various embodiments ofthe present disclosure.

FIG. 10 is a flow chart illustrating an algorithm for implementingmethods in accordance with various embodiments of the presentdisclosure.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

Embodiments of the present disclosure may describe configurations ofvarious components of a laser printing device architecture andassociated techniques. In the following detailed description, referenceis made to the accompanying drawings which form a part hereof whereinlike numerals designate like parts throughout, and in which is shown byway of illustration embodiments in which the disclosure may bepracticed. It is to be understood that other embodiments may be utilizedand structural or logical changes may be made without departing from thescope of the present disclosure. Therefore, the following detaileddescription is not to be taken in a limiting sense, and the scope ofembodiments in accordance with the present disclosure is defined by theappended claims and their equivalents.

The description below includes use of perspective-based descriptionssuch as bottom. Such descriptions are merely used to facilitate thediscussion and are not intended to restrict the application ofembodiments of the present disclosure.

For the purposes of the present disclosure, the phrase “A/B” means A orB. For the purposes of the present disclosure, the phrase “A and/or B”means “(A), (B), or (A and B).” For the purposes of the presentdisclosure, the phrase “at least one of A, B, and C” means “(A), (B),(C), (A and B), (A and C), (B and C), or (A, B and C).”

The description incorporates use of the phrases “in an embodiment,” or“in embodiments,” which may each refer to one or more of the same ordifferent embodiments. Furthermore, the terms “comprising,” “including,”“having,” and the like, as used with respect to embodiments of thepresent disclosure, are synonymous.

As used herein, the term “module” may refer to, be part of, or includean Application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group) and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablecomponents that provide the described functionality.

FIG. 1 is a schematic diagram of a laser printing device 100, inaccordance with various embodiments of the present disclosure. Laserprinting device 100 includes a housing 102, a laser module 104, anoptical photoconductor (OPC) 106, a cartridge 108, a transfer mechanism110, a fuser 112, an area array complementary metal-oxide-semiconductor(CMOS) image sensor 114, an illumination source 116, a transparentsurface 118, an input tray 120, a pick mechanism 122, guides 124, and acover/output tray 126. According to various embodiments, laser printingdevice 100 may include more or less components than depicted.

Laser printing device 100 includes housing 102 to substantially coverone or more components of the laser printing device 100, such as, forexample, components of a printing assembly or copying assembly. Housing102 substantially protects components within the housing 102 fromexposure to undesirable elements such as light, dust, or other debris,and may also protect unsightly or dangerous mechanisms of the laserprinting device 100 from a user's view or touch. In an embodiment,housing 102 includes a substantially flat surface 128, to facilitateplacement of the laser printing device 100 on a substantially flatsurface external to the laser printing device 100.

In the depicted embodiment of FIG. 1, laser printing device 100 includesa laser module 104 for laser printing technology. Laser module 104includes one or more laser diodes (not shown) or light emitting diodes(LEDs) (not shown) that generate a laser 105 to project an image onto aphotoconductor such as OPC 106. As used herein, laser diodes, LEDs,lasers and laser beams may be used interchangeably to generally refer tolasers utilized in laser printing within laser printing device 100. OPC106 can comprise, for example, an electrically charged rotating drum.OPC 106 is accompanied by a cartridge 108. Cartridge 108 protects OPC106 and/or provides other functionality associated with laser printingsuch as, for example, associated optics or mirrors for scanning or beamalignment.

Laser 105 alters a charge on areas of OPC 106 according to a desiredimage, whereupon particles such as dry ink or toner areelectrostatically attracted to the OPC 106 according to the desiredimage. OPC 106 is pressed or rolled over one or more print mediums attransfer mechanism 110. Fuser 112 applies heat and pressure to bond thedry ink or toner to the one or more print mediums. One or more printmediums may comprise paper in one or more embodiments, but is notlimited in this regard and may include other printing media in otherembodiments—e.g., transparency film, and so on.

In FIG. 1, an example printing path 130 is indicated by associateddirectional arrows. Printing path 130 is a path through laser printingdevice 100 that a print medium follows while undergoing a printingprocess. Laser printing device 100 includes input tray 120 to receive orhold one or more print mediums for printing by a printing assembly oflaser printing device 100. Pick mechanism 122 moves the one or moreprint mediums through printing path 130 to undergo printing actionsincluding, for example, the actions described with respect to lasermodule 104, OPC 106, transfer mechanism 110, and/or fuser 112. Guides124 guide the one or more print mediums to cover/output tray 126.Cover/output tray 126 can be a dual purpose structure configured tocover an adjacent transparent surface 118 used for copying and alsoconfigured to serve as an output tray for one or more printed printmediums.

In some embodiments, laser printing device 100 comprises a copyingassembly having an area array CMOS image sensor 114 and an illuminationsource 116 disposed within the housing 102. The copying assembly can beintegrated to share a same area as a printing assembly in one or moreembodiments. For example, area array CMOS image sensor 114 andillumination source 116 of the copying assembly can share an area oflaser printing device 100 with components of a printing assembly such aslaser module 104, OPC 106, and/or transfer mechanism 110.

Area array CMOS image sensor 114 is intended to represent a variety ofimage sensors such as those that are widely employed, for example, inthe use of cell phone cameras. Area array CMOS image sensor 114 is alsoreferred to herein as a full array, area array, or CMOS image sensor, orcombinations thereof. In an embodiment, CMOS image sensor comprises anactive pixel sensor (APS). Hereinafter, area array CMOS image sensor 114is referred to as “CMOS image sensor” 114. The term “CMOS”, as used inthe phrase “CMOS image sensor” herein, may refer to a commonly usedtrade name of an image sensor type to distinguish the image sensor fromother types of image sensors such as, for example, linear array contactimage sensor (CIS) and/or charge coupled device (CCD) sensors.

Although the term “CMOS” may conventionally refer to a particularmanufacturing process to form a device from various materials, the termCMOS as used within this description is not limited to any particularmanufacturing process. For example, the phrase“metal-oxide-semiconductor” in the term “CMOS” may conventionally referto a physical structure of field-effect transistors where a metal gateis formed on an oxide material, which is formed on a semiconductor.Materials other than traditional metals, oxides, and semiconductors maybe employed to form analogous devices in emerging semiconductortechnologies, however such physical structure may still be referred toas a CMOS device by convention or trade usage. Similarly, “CMOS” as usedherein is intended to include image device sensors, for example, thatare formed according to emerging semiconductor technologies that utilizesuch different material structures.

CMOS image sensor 114 is configured to capture one or more images forcopying. In an embodiment, CMOS image sensor 114 is configured tocapture an entire image of a document at once. For example, CMOS imagesensor 114 may not require scanning of one or more documents to capturean image as used in linear array technologies. In an embodiment, CMOSimage sensor 114 comprises an optical path 132 that allows image captureof one or more objects placed on a transparent surface 118 of laserprinting device 100.

A copying assembly of laser printing device 100 further comprises asubstantially flat transparent surface 118 disposed in an optical path132 of CMOS image sensor 114 to support an object for image capture bythe CMOS image sensor 114. An object for image capture may comprise avariety of articles including, for example, one or more documents,photographs, or three-dimensional objects. Substantially flattransparent surface 118 can comprise glass, plastic, or any othersuitable material to provide a substantially flat, transparent surfacefor imaging/copying.

In an embodiment, the substantially flat transparent surface 118 of thecopying assembly is substantially parallel with the substantially flatsurface 128 of the housing 102. CMOS image sensor 114 is disposedbetween the substantially flat transparent surface 118 of the copyingassembly and the substantially flat surface 128 of the housing 102,within an area of the housing 102 where the printing assembly isdisposed.

Laser printing device 100 further comprises a cover 126 coupled to thelaser printing device 100 such that cover 126 can move to an “open”position and a “closed” position. In the open position, cover 126substantially exposes transparent surface 118; and in the closedposition, cover 126 substantially covers the transparent surface 118.Cover 126 can further be configured to function as an output tray forone or more printed documents in the closed position. For example,guides 124 can output a printed document onto a surface of cover 126. Aprinted document can be removed by a user, for example, before cover 126is opened.

Laser printing device 100 further includes an interlock 134 operativelycoupled with cover 126 and configured to disable laser module 104 whencover 126 is in an open position. Interlock 134 can comprise amechanical or electrical interlock, or combinations thereof, accordingto one or more embodiments. Interlock 134 can comprise a same mechanismto disable laser module 104 that may be used when laser printing device100 is opened for maintenance or troubleshooting purposes including, forexample, changing a cartridge 108 or clearing a paper jam. In one ormore embodiments, transparent surface 118 further comprises a filtercoating to block laser light of laser module 104 from exiting throughtransparent surface 118 of the copying assembly. Combinations of suchfeatures may be implemented according to various embodiments. Suchfeatures may increase safety of using laser printing module 104 bypreventing or reducing laser exposure through transparent surface 118.

A variety of features may be implemented in laser printing device 100 toprotect OPC 106 from excessive light exposure. In an embodiment, OPC 106is configured to rotate when cover 126 is in the open position and/orwhen illumination source 116 is enabled to reduce localized overexposureof OPC 106 to ambient or illuminative light. Laser printing device 100further comprises a shade structure 136 operatively coupled with cover126 to prevent or reduce exposure of OPC 106 to ambient light when cover126 is in the open position. For example, an interlock 134 can indicatethat cover 126 is open, which may cause a signal to be sent to moveshade structure 136 into a position that protects OPC 106 from lightthat may enter through transparent surface 118. Shade structure 126comprises a shutter mechanism in an embodiment.

Laser printing device 100 further comprises an illumination source 116disposed within housing 102. Illumination source 116 can comprise any ofa variety of light sources to provide sufficient light to allow imagecapture by CMOS image sensor 114. In an embodiment, illumination source116 includes one or more light-emitting diodes (LEDs) and/or coldcathode fluorescent lamps (CCFLs) and can include one or more color orwhite lights.

FIG. 2 schematically illustrates a printing arrangement 200 for use witha laser printing device 100 of FIG. 1. Printing arrangement 200 mayinclude laser module 104 and OPC 106, as well as other components.Printing arrangement 200 includes a controller chip 202 that includes amicroprocessor 204. Microprocessor 204 is coupled to a bus 206 that iscoupled to a memory controller 208, all of which are also included oncontroller chip 202. Memory controller 208 is coupled to an externalmemory 210 that may be in the form of double data rate (DDR) memory.External memory 210 is included on a circuit board 212 that alsoincludes controller chip 202. External memory 210 may, in variousembodiments, be included on a separate circuit board from controllerchip 202. Controller chip 202 also includes an input/output (I/O)interface 214, which is also coupled to bus 206. I/O interface 214 iscoupled to a USB port 216 that is included on circuit board 212. USBport 216 may be used to couple printing arrangement 200, thereby laserprinting device 100, to a computing device (not shown), and/or some typeof network. Other types of ports besides USB port 216 are also possiblein various embodiments.

Controller chip 202 also includes at least one video channel 218 that iscoupled via laser coupling line 220 to a laser array 222. Laser array222 includes laser diodes 224A-224D. In the exemplary embodimentillustrated in FIG. 2, laser array 222 includes four laser diodes224A-224D. More or fewer laser diodes may be included and the presentdisclosure is not limited in this regard. Depending upon the number oflaser diodes included with laser array 222, a corresponding number ofvideo channels 218 are included on controller chip 202. Thus, in theexemplary embodiment illustrated in FIG. 2, controller chip 202 includesfour video channels 218, where each video channel 218 corresponds to aparticular laser diode 224A-224D. For clarity and simplicity, only onevideo channel 218 is illustrated in FIG. 2.

Printing arrangement 200 further includes a mirror 226 and an organicphotoconductor (OPC) 228. During operation of printing arrangement 200,mirror 226 continually rotates in a direction indicated by A and OPC 228continually rotates in a direction indicated by B in FIG. 2. Laserdiodes 224A-224D fire at mirror 226, which then reflects the resultinglasers, as indicated by the phantom lines, onto OPC 228. The continuallyrotating mirror 226 deflects the lasers across the surface of OPC 228.The mirror continues to rotate in the direction A thereby moving thereflected lasers axially along OPC 228, as indicated by the phantomlines. Once the lines of pixel data for laser diodes 224A-224D arecompleted, the lasers will reach an edge of one facet or side of mirror226. When the lasers start to reflect off of the next facet of mirror226, the reflected lasers will travel along the phantom lines onto OPC228 and move axially along OPC 228 (due to the continued rotation of themirror 226), but at new positions on OPC 228 due to the rotation of OPC228. The distance the constantly rotating OPC 228 has rotated betweenswitching between facets of mirror 226 will set the amount of overlap orgap between the sets of lines created by the lasers and the rotatingmirror 226. The print medium (not shown) moves past and relative to theOPC 228 to print the image onto the print medium.

Referring to FIG. 3, each video channel 218 includes a direct memoryaccess (DMA) module 302 that provides raw pixel data to a video pipelinemodule 304 that is included within each video channel 218. Videopipeline module 304 converts the raw pixel data to lines of pixel data,which is then provided to a shared line rendering hardware block module306 that is included within each video channel 218. Shared linerendering hardware block module 306 will create shared lines of pixeldata for two or more of laser diodes 224A-224D, as will be described infurther detail herein. The shared lines of pixel data and the lines ofpixel data are then forwarded to a data serializer module 308 includedwithin each video pipeline 218, which serializes the lines of pixel dataand the shared lines of pixel data, and provides the lines of pixel dataand the shared lines of pixel data to laser array 222 and the particularlaser diode of laser diodes 224A-224D that corresponds to the particularvideo channel 218.

In accordance with various embodiments, the video pipelines 218 areincluded within an application-specific integrated circuit (ASIC) ofcontroller chip 202. Other components within controller chip 202 may ormay not be included within the same ASIC as video channels 218,depending upon the application.

In order to print an image, memory controller 208 retrieves an image tobe printed from memory 210. Alternatively, an image may be retrieved viaUSB port 216 and I/O interface 214 and provided to microprocessor 204.In either case, the image to be printed is provided to the videochannels 218. The image to be printed is provided in the form of rawpixel data. The video channels 218 then convert the raw pixel data intolines of pixel data corresponding to a particular laser diode 224 to befired and thereby create lasers at mirror 226, which reflects the laserstowards the OPC 228. Alternatively, the data may be retrieved as linesof pixel data and shared lines of pixel data, in which case theoperation of the video channels 218 may be simplified and eveneliminated.

As previously described, FIG. 4 schematically represents a set ofprinted lines 400 created by sweeps of lasers from laser diodes 224. Inthe example of FIG. 4, eight laser diodes 224 are included within laserprinting device 100. In the example to be described herein fordescribing embodiments of the present disclosure with respect to FIGS.4-9, laser printing device 100 includes eight laser diodes 224 and thus,eight video channels 218. More or less laser diodes 224 and videochannels 218 may be included in laser printing device 100 and thepresent disclosure isn't limited in this regard.

As previously described, the printed lines of set 400 are represented bylines 1-8. As may be seen at 402, a gap is present from the eighthprinted line created by the eighth laser diode during a first sweep ofthe lasers and the first printed line from a first laser diode in asecond sweep of the lasers. At 404, an overlap is present between lineeight created by the eighth laser diode and the first printed line ofthe first laser diode between the second sweep of the lasers and a thirdsweep of the lasers. Because of such gaps or overlaps, printed imagescan have various visual artifacts and defects visible to the naked eyewhere these gaps and overlaps occur.

In accordance with the various embodiments of the present disclosure, inorder to significantly reduce artifacts attributable to gaps andoverlaps between sweeps of the lasers from the laser diodes 228, two ormore lasers from the laser diodes 224 intentionally overlap theirrespective printing of pixel data between sweeps of the lasers. Forexample, in the present example, the laser array 222 includes eightlaser diodes 224 that produce eight lasers, yet only seven lines fromthe lasers advance with each sweep of the lasers over the OPC 228, asopposed to the prior art method of advancing all eight lines. Thus, thefirst and last printed line of each sweep of the lasers are overlappedby two lasers; in this example, the bottom laser of one sweep and thetop laser of another sweep.

In accordance with the present disclosure, the lines of data for the toplaser and the bottom laser are digitally alternated such that the toplaser and bottom laser do not try and render the same portion of aprinted line, but are coordinated such that they each only renderportions of the printed line. However, when the portions of the line arecombined, the combined portions recreate all of the data for the printedline. Such sharing and overlapping of the top and bottom lasers reducethe artifacts and visual defects created at the printed lines of theprinted image created by the overlapping lasers.

In accordance with the various embodiments, a method for creating theoverlap between the lasers is to alternate pixels, i.e., even pixels forone laser and odd pixels for the other laser for each line of pixel datathat is to be used for the overlapping of lasers. This requires takinglines of pixel data that are to be used for the overlapping of lasersand creating shared lines of pixel data. Thus, during one sweep or passof the lasers, the bottom laser diode will fire during the even pixelsto begin printing an overlapped line in an image to be printed andduring the next sweep of the lasers, the top laser diode will fire tocomplete printing of the overlapped line in the image to be printed.

FIG. 5 schematically illustrates how forcing an overlap and alternatingthe data between the overlapped lasers looks with the same gap error 402and overlap error 404. As can be seen, the gap and overlap are no longerpositioned at a same location across the entire image. By breaking upthis gap or overlap, the visual artifacts and defects of a printed imagemay be less noticeable to the naked eye. The area 502 now represents thegap area previously illustrated in FIG. 4 at 402, while the area 504represents the overlap area 404 of FIG. 4. As can be seen, theindividual blocks 8 at 502 represent a first sweep of the lasers wherethe eighth laser is fired to produce pixels, while the blocks 1 at 502represent where the first laser is fired to produce pixels in the secondsweep of the lasers. This completes printing of a first shared line ofdata at 502 within the printed image. The individual blocks 8 at 504represent the second sweep of the lasers where the eighth laser is firedto produce pixels, while the blocks 1 at 504 represent where the firstlaser is fired to produce pixels in a third sweep of the lasers. Thiscompletes printing of a second shared line of data at 502 within theprinted image.

FIG. 6 illustrates a graph of desired output for a single(non-overlapped) laser versus time and the same data alternately beingoutput to two separate overlapping lasers (Pass N and Pass N+1). Thus,line 600 represents an unaltered line of pixel data. Lines 602 and 604,together, represent a shared line of pixel data. While the graph in FIG.6 illustrates lines 602 and 604 coincidentally, thus implying that lines602 and 604 are alternatingly produced on the same pass (sweep), thelasers actually do not produce the data during the same sweep of thelasers, so lines 602 and 604 are outputting on different sweeps (orpasses) of the lasers. However, lines 602 and 604 are illustrated inFIG. 6 coincidentally so that one can see how lines 602 and 604reconstruct the original line of pixel data represented by line 600. InFIG. 6, a high output indicates that the laser is turned on (firing) anda low value indicates that the laser is turned off (not firing). Thehorizontal areas of the graph for each pixel represent the time forexecuting pixel data related to each pixel.

As is known in the art, there are four pixel descriptions with respectto firing of laser diodes for various pixels versus time. Moreparticularly, the types include centered, left justified, rightjustified and split. Thus, data for each pixel may involve executingsome the data partially outside of the time for the pixel illustrated inthe graph. In FIG. 6, pixels 2, 4, and 5 are “split” with equal ornearly equal pulses located on the left and right side of the pixeltime. Pixel 6 is left justified having only a single pulse on the leftside of the pixel time. Pixels 2, 5 and 6 represent narrow pulses thatif these pixel times had no pulses on either side of them, they might betoo narrow to reproduce. Many laser systems have a minimum laser on-timefor the laser diodes. Thus, for such systems, the minimum laser on-timecould be violated if the data is arbitrarily divided between the twolaser diodes. For instance, a pixel that generates a full-on pulse of alaser diode, followed by a left justified pixel can result in a singleoutput pulse of the laser diode. The left justified pixel can be a veryshort pulse (when viewed as a single pixel), but to the laser diode, itis simply the previous pulse extended by a small amount. If these twoadjacent (and connected) pulses were separated between two laser diodes,the full-on pulse would be fine for the first laser diode, but thenarrow left justified pulse may violate a minimum laser on-time for thesecond laser diode and thus, may not be able to be produced on its ownby the second laser diode.

Thus, in accordance with various embodiments, the method for creatingthe overlap between the lasers can include starting with a first pulsefor a first laser and if a subsequent pulse can be performed by a secondlaser without any timing violations, then the subsequent pulse can beperformed by the second laser. Data would be identical for each of theoverlapping lasers, so as long as the overlapping lasers have differentstarting conditions, such a method works out well. Thus, for two lasers,the first laser is assigned the first pixel and the second laser waitsfor a condition that allows the second laser to be assigned a pixel andto thereby begin operation in a subsequent sweep of the lasers.

Referring again to FIG. 6, the shaded areas of lines 602 and 604illustrate which laser pass gets to reproduce the incoming data based onthe currently described embodiment for assigning pixels to the lasers inthe shared line of pixel data. If a first laser is outputting the dataon Pass N with pixel 1, it will also output pixels 2 and 3 since pixel 2requires a pulse next to it on both adjacent pixels. If this pattern ofpixel 1 (laser diode full-on) and pixel 2 (split narrow pixel)continues, there might never be a condition that would allow atransition to an alternate laser.

To address the possibility of never transitioning to an alternate laser,in accordance with various embodiments, each pixel is split into twoequal pixels or half pixels. As may be seen in FIG. 7, each half pixelincludes only a single pulse for a laser. With such a method, the datafrom a line of pixel data can now be split between the two passes andboth lasers will be alternating back and forth frequently. As previouslymentioned with the embodiment of the method prior to splitting thepixels, the method includes allowing the laser to take over as soon aspossible. For simplicity, the method can ignore whether there isactually data to output. Thus, with reference to FIG. 7, the two lasersalternate even when outputting no pulse. Accordingly, for Pass N, alaser fires at 710 and the pulse is complete at the half pixel of pixel1 indicated by 712. The shared line of pixel data switches to the secondlaser and during Pass N+1, the second laser fires at 714. Because thepulse is not complete at the end of the second half of pixel 1 at 716,the second laser continues to fire into the first half pixel of pixel 2at 718. During the first half of pixel 2, the pulse ends and thus,during the second half of pixel 2 at 720, and during Pass N, the firstlaser fires, with this pulse continuing through the first half of pixel3 and ending at the first half of pixel 3 at 722. As can be seen, thispattern continues such that a shared line of data is created during PassN and Pass N+1 by the two lasers. As can be seen at pixels 6 and 7, theswitch occurs at each half pixel, even if there is no data to be output.

Since the shared line of pixel data will alternate between the lasers atthe half pixel points as long as a laser is not firing at that point,some patterns within a shared line of pixel data may result in only asingle laser ever firing. An example of such a pattern can be seen inFIG. 8. In the example, the data and the line of pixel data onlyrequires a pulse from a laser at the beginning of each pixel, i.e., atthe first half pixel for each pixel. Thus, as can be seen, during PassN, the first laser will fire at the beginning of pixels 1, 3, 5, 6 and7. Since the first pixel is not firing at the half pixel mark in each ofpixels 1-7, the shared line of data results in switching to the secondlaser for Pass N+1 at the second half of each pixel 1-7. However, thereis no data to be output with the shared line of pixel data during thesecond half of each pixel 1-7 and thus, during Pass N+1, the secondlaser never fires.

Accordingly, in accordance with various embodiments, the method can bealtered such that a further requirement for switching to a laserrequires that a laser have fired prior to switching to the other laser.Thus, as may be seen in FIG. 9, the line of pixel data is rendered intoa shared line of pixel data such that during Pass N, during the firsthalf of pixel 1 at 900, the first laser fires. Since the pulse of thefirst laser is complete by the end of the first half of pixel 1 at 902,the shared line of pixel data switches to the second laser for executionduring Pass N+1. However, during the second half of pixel 1 and pixel 2,the second laser does not fire. Thus, when the next pulse is requiredduring the first half of pixel 3 at 904, the second laser fires duringPass N+1. At the end of the first half of pixel 3 at 906, the pulseexecuted by the second laser during Pass N+1 is complete and thus, theshared line of pixel data switches at 908 so that the first laser takesover during the Pass N until it finally executes a pulse during thefirst half of pixel 5 at 910. In summary, the first half of pixel 1generates a pulse by a laser, and thus, the next half pixel can behanded to a subsequent laser. The second half of pixel 1 does notgenerate a pulse, so the laser continues to look for something to do anddoes not hand off to the first laser since it has not yet generated apulse. The first pulse generated by the second laser is at the firsthalf of pixel 3 and thus, when this pulse is complete, the second halfof pixel 3 can be handed back to the first laser.

FIG. 10 represents a flow chart for implementing an algorithm that canbe implemented in the video channels 218 for the lasers 224 that willexecute shared lines of pixel data. In the present example, two channels(two lasers) will be used to print shared lines of pixel data whenprinting an image. More lasers and channels may be used if desired. At1000, the algorithm begins by selecting a desired start channel and theindex for the beginning of the shared line of pixel data is the firsthalf pixel of pixel 1, with the generated_pulse variable set to zero. At1002, the algorithm checks to see if the channel is equal to theselected channel. If it is, then at 1004, the laser diode outputs datafor the half pixel. If at 1002 the channel does not equal the selectedchannel, then the output is set to 0 so there is no output data on thecorresponding laser at 1006. At block 1008, the algorithm checks theoutput data to see if the half pixel contains a pulse. If the half pixelcontains a pulse does, then at 1010 the generated_pulse variable is setto 1 to indicate a pulse was output to a laser and then the index isincremented at 1012. If the half pixel does not contain a pulse, thenthe index is incremented at 1012. At 1014, the algorithm checks to seeif a pulse has been generated. If it has, then at block 1016, thealgorithm checks to make sure that the next half pulse can be executedby another channel (laser) without violating any minimum standards forthe laser (i.e., that the next pulse can be “runt” free). If the nexthalf pulse can be executed properly by the next laser, then at block1018, the next channel (laser) is selected and the generated pulsebecomes zero. If at 1016, the next half pulse cannot be generated runtfree, then the channel remains the same. At block 1020, the algorithmchecks the index to see if the end of the shared line of data has beenreached. If the end of the shared line of data has been reached, thenthe shared line of data has been completed. If the shared line of datais not at the end, then the algorithm returns to block 1002.

Since the same shared lines of pixel data will be presented to more thanone laser channel at different times (i.e., during different sweeps ofthe lasers), each laser channel includes an algorithm similar to thatdescribed in FIG. 10. In the example of FIGS. 4-10, there are only twochannels that create the shared lines of data, channel 0 and channel 1.Either channel could include 0 as the start channel. Thus, at 1000 and1018, the select equal next channel just toggles between 0 and 1. For atwo laser overlap, the next channel would just toggle between the twooverlapped channels. Many sequences are acceptable and thus, the presentdisclosure is not limited in this regard.

For hardware implementation, all video channels 218, as previouslydescribed, are generally constructed as identical video channels suchthat each video channel 218 responds to the channel selection as beingchannel zero. Thus, the separation of data among the video channels 218requires programming different starting values for each video channel218. For example, the first video channel 218 can be started with zeroand the other channels can start with different channel numbers so thatall video channels 218 do not output the same data.

In accordance with various embodiments, it should be noted that thefirst and last lines of an image to be printed will be exceptions forthe shared rendering or use of shared lines of pixel data. For example,in the eight laser system example described in conjunction with FIGS.4-10, channel zero (the first laser) and channel seven (the last laser)would be the video channels that utilize shared lines of pixel data.However, for an image to be printed, the first line of the image willnot have the last laser overlapping in a subsequent pass. Accordingly,the first line of the image to be printed needs to be printed in itsentirety by the first laser. Likewise, the last line of the image to beprinted will not have the first laser overlapping with the last laserand therefore, the last laser needs to render all of the last line ofthe image to be printed. While this exception is not detailed in thealgorithm flowchart of FIG. 10, the exception may be added to the firstdecision diamond 1002 such that the condition could be changed to(channel=select) or (first_line AND all_first_line) OR (last_line ANDall_last_line). With the addition of two more programmable selects:all_first_line and all_last_line, the output data block 1004 is set upto output all the data for the first or last line. Alternatively, thefirst line of the image to be printed may begin with a line printed bythe second laser during a first pass of the lasers, while the last lineof the image to be printed may be printed with the seventh laser duringa final pass of the lasers.

Referring back to FIG. 3, as previously noted, DMA module 302 retrievesimage data for an image to be printed from the system memory 210 (or viathe I/O interface 214). DMA module 302 passes the individual pixel datato video pipeline module 304, which processes the individual pixel datainto lines of pixel data. In addition to the pixel data, DMA module 302also sends information to the downstream hardware to indicate the startof an image to be printed, the end of a line, and the end of an image tobe printed. Shared line rendering hardware block 306 utilizes thisinformation to indicate the first and last line of an image to beprinted and when a line for a laser has finished printing.

Video pipeline module 304, in some embodiments, may apply some form ofmodification to the pixel data, such as changing the pixel size or thepixel type (left, right, center, split). The configuration informationused by video pipeline module 304 must be identical for shared linerendering hardware modules 306 in each video channel 218 so that thesame modifications are performed on the pixel data.

Shared line rendering hardware module 306 then processes the lines ofpixel data by either passing the lines of pixel data straight through todata serializer module 308 (for lasers 224 that are not utilizing sharedlines of pixel data), and creating shared lines of pixel data for lasers224 that are utilizing shared lines of pixel data. The shared lines ofpixel data are passed along, along with the unaltered lines of pixeldata, from shared line rendering hardware module 306 to data serializermodule 308. Data serializer module 308 serializes the multi-bit pixeldata lines and then passes the serialized lines of pixel data to laserdiode 224 that corresponds to the video channel 218. Lasers 224 thenfire accordingly.

Thus, one or more of DMA modules 302, video pipeline modules 304, sharedline rendering hardware modules 306 and data serializer modules 308 mayform a processing module. Additionally, one or more of DMA modules 302,video pipeline modules 304, shared line rendering hardware modules 306,data serializer modules 308 and microprocessor 204 may serve as or forma controller to facilitate control of a laser printing device 100.

Various operations may have been described as multiple discrete actionsor operations in turn, in a manner that is most helpful in understandingthe claimed subject matter. However, the order of description should notbe construed as to imply that these operations are necessarily orderdependent. In particular, these operations may not be performed in theorder of presentation. Operations described may be performed in adifferent order than the described embodiment. Various additionaloperations may be performed and/or described operations may be omittedin additional embodiments.

Although certain embodiments have been illustrated and described herein,a wide variety of alternate and/or equivalent embodiments orimplementations calculated to achieve the same purposes may besubstituted for the embodiments illustrated and described withoutdeparting from the scope of the present disclosure. This application isintended to cover any adaptations or variations of the embodimentsdiscussed herein. Therefore, it is manifestly intended that embodimentsin accordance with the present disclosure be limited only by the claimsand the equivalents thereof.

What is claimed is:
 1. A method comprising: providing pixel datacorresponding to an image to be printed on a print medium, wherein thepixel data comprises lines of pixel data and shared lines of pixel data,the shared lines of pixel data comprising pixels that are split intohalf pixels, the shared lines of pixel data configured such that a firstlaser and a second laser of a plurality of lasers within a laserprinting arrangement will print the shared lines of pixel data duringprinting of the image on the print medium, wherein the shared lines ofpixel data comprises a first shared line of pixel data, wherein thefirst shared line of pixel data comprises a plurality of sections,wherein the plurality of sections comprise a first group of sections anda second group of sections, wherein each section of the first group ofsections results in only a single pulse for the first laser, whereineach section of the second group of sections results in only a singlepulse for the second laser, and wherein a section of the first group ofsections is interleaved between two corresponding sections of the secondgroup of sections; and printing the image, including repeatedly movingthe plurality of lasers and the optical photoconductor (OPC) relative toone another, while moving the plurality of lasers and the OPC relativeto one another, firing the plurality of lasers in accordance with thelines of pixel data and the shared lines of pixel data, and moving theprint medium and the OPC relative to one another, wherein during movingof the plurality of lasers and the OPC medium relative to one another,the first laser fires in accordance with lines of the shared lines ofpixel data and the second laser fires in accordance with lines of theshared lines of pixel data, the firing of the second laser beginningprinting of lines of the image and the firing of the first lasercompleting printing of lines of the image.
 2. The method of claim 1,wherein providing pixel data corresponding to an image to be printed ona print medium comprises: providing, to an apparatus, the pixel data;the apparatus modifying the pixel data to create lines of pixel data;and the apparatus modifying some lines of the pixel data to create theshared lines of pixel data.
 3. The method of claim 1, wherein: during afirst moving of the plurality of lasers and the OPC relative to oneanother, the first laser fires in accordance with an entire first lineof pixel data to print a first line of the image and the second laserfires in accordance with a first line of the shared lines of pixel datato begin printing another line of the image; and during a final movingof the plurality of lasers and the OPC relative to one another, thesecond laser fires in accordance with an entire final line of pixel datato print a final line of the image and the first laser fires inaccordance with a final line of the shared lines of pixel data tocomplete printing of a penultimate line of the image.
 4. The method ofclaim 1, wherein the first group of sections and the second group ofsections are assigned to the first laser and to the second laser basedupon half pixels.
 5. An apparatus comprising: a processing moduleconfigured to receive pixel data corresponding to an image to be printedon a print medium, wherein the pixel data is arranged into lines ofpixel data and shared lines of pixel data, the shared lines of pixeldata comprising pixels that are split into half pixels, the shared linesof pixel data configured such that a first laser and a second laser of aplurality of lasers within a laser printing arrangement will print theshared lines of pixel data during printing of the image on the printmedium, wherein the shared lines of pixel data comprises a first sharedline of pixel data, wherein the first shared line of pixel datacomprises a plurality of sections, wherein the plurality of sectionscomprise a first group of sections and a second group of sections,wherein each section of the first group of sections results in only asingle pulse for the first laser, wherein each section of the secondgroup of sections results in only a single pulse for the second laser,and wherein a section of the first group of sections is interleavedbetween two corresponding sections of the second group of sections; acontroller configured to control printing of the image, the printing ofthe image comprising repeatedly moving the plurality of lasers and anoptical photoconductor (OPC) relative to one another, while moving theplurality of lasers and the OPC relative to one another, firing theplurality of lasers in accordance with the lines of pixel data and theshared lines of pixel data, and moving the print medium and the OPCrelative to one another, wherein during moving of the plurality oflasers and the OPC relative to one another, the first laser fires inaccordance with lines of the shared lines of pixel data and the secondlaser fires in accordance with lines of the shared lines of pixel data,the firing of the second laser beginning printing of lines of the imageand the firing of the first laser completing printing of lines of theimage.
 6. The apparatus of claim 5, wherein: the processing module isfurther configured to modify the pixel data to create the lines of pixeldata; and the processing module is further configured to modify somelines of the pixel data to create the shared lines of pixel data.
 7. Theapparatus of claim 5, wherein the controller is further configured suchthat: during a first moving of the plurality of lasers and the OPCrelative to one another, the first laser fires in accordance with anentire first line of pixel data to print a first line of the image andthe second laser fires in accordance with a first line of the sharedlines of pixel data to begin printing another line of the image; andduring a final moving of the plurality of lasers and the OPC relative toone another, the second laser fires in accordance with an entire finalline of pixel data to print a final line of the image and the firstlaser fires in accordance with a final line of the shared lines of pixeldata to complete printing of a penultimate line of the image.
 8. Theapparatus of claim 5, wherein the first group of sections and the secondgroup of sections are assigned to the first laser and to the secondlaser based upon half pixels.
 9. The apparatus of claim 5, wherein theapparatus includes an Application-Specific Integrated Circuit (ASIC)that includes the processing module.
 10. A printer comprising: a lasermodule comprising a plurality of lasers; an optical photoconductor; aprint medium transport path adjacent to the optical photoconductor; andan apparatus comprising a processing module configured to receive pixeldata corresponding to an image to be printed on a print medium, whereinthe pixel data is arranged into lines of pixel data and shared lines ofpixel data, the shared lines of pixel data comprising pixels that aresplit into half pixels, the shared lines of pixel data configured suchthat a first laser and a second laser of the plurality of lasers willprint the shared lines of pixel data during printing of the image on theprint medium, wherein the shared lines of pixel data comprises a firstshared line of pixel data, wherein the first shared line of pixel datacomprises a plurality of sections, wherein the plurality of sectionscomprise a first group of sections and a second group of sections,wherein each section of the first group of sections results in only asingle pulse for the first laser, wherein each section of the secondgroup of sections results in only a single pulse for the second laser,and wherein a section of the first group of sections is interleavedbetween two corresponding sections of the second group of sections, anda controller configured to control printing of the image, the printingof the image comprising repeatedly moving the plurality of lasers and anoptical photoconductor relative to one another, while moving theplurality of lasers and the optical photoconductor relative to oneanother, firing the plurality of lasers in accordance with the lines ofpixel data and the shared lines of pixel data, and moving the printmedium along the print medium path past the optical photoconductor,wherein during moving of the plurality of lasers and the opticalphotoconductor relative to one another, the first laser fires inaccordance with lines of the shared lines of pixel data and the secondlaser fires in accordance with lines of the shared lines of pixel data,the firing of the second laser beginning printing of lines of the imageand the firing of the first laser completing printing of lines of theimage.
 11. The printer of claim 10, wherein: the processing module isfurther configured to modify the pixel data to create the lines of pixeldata; and the processing module is further configured to modify somelines of the pixel data to create the shared lines of pixel data. 12.The printer of claim 10, wherein the controller is further configuredsuch that: during a first moving of the plurality of lasers and theoptical photoconductor relative to one another, the first laser fires inaccordance with an entire first line of pixel data to print a first lineof the image and the second laser fires in accordance with a first lineof the shared lines of pixel data to begin printing another line of theimage; and during a final moving of the plurality of lasers and theoptical photoconductor relative to one another, the second laser firesin accordance with an entire final line of pixel data to print a finalline of the image and the first laser fires in accordance with a finalline of the shared lines of pixel data to complete printing of apenultimate line of the image.
 13. The printer of claim 10, wherein thefirst group of sections and the second group of sections are assigned tothe first laser and to the second laser based upon half pixels.
 14. Theprinter of claim 10, wherein the apparatus includes anApplication-Specific Integrated Circuit (ASIC) that includes theprocessing module.